Data communication networks may include various computers, servers, nodes, routers, switches, bridges, hubs, proxies, and other network devices coupled to and configured to pass data to one another. These devices will be referred to herein as “network elements.” Data is communicated through the data communication network by passing protocol data units, such as Internet Protocol packets, Ethernet Frames, data cells, segments, or other logical associations of bits/bytes of data, between the network elements by utilizing one or more communication links between the network elements. A particular protocol data unit may be handled by multiple network elements and cross multiple communication links as it travels between its source and its destination over the network.
The various network elements on the communication network communicate with each other using predefined sets of rules, referred to herein as protocols. Different protocols are used to govern different aspects of the communication, such as how signals should be formed for transmission between network elements, various aspects of what the protocol data units should look like, how protocol data units should be handled or routed through the network by the network elements, and how information such as routing information should be exchanged between the network elements.
Ethernet is a well known networking protocol that has been defined by the Institute of Electrical and Electronics Engineers (IEEE) as standard 802.1 in Ethernet network architectures, devices connected to the network compete for the ability to use shared telecommunications paths at any given time. Where multiple bridges or nodes are used to interconnect network segments, multiple potential paths to the same destination often exist. The benefit of this architecture is that it provides path redundancy between bridges and permits capacity to be added to the network in the form of additional links. However to prevent loops from being formed, a spanning tree was generally used to restrict the manner in which traffic was broadcast or flooded on the network. A characteristic of a spanning tree is that there is only one path between any pair of destinations in the network, and therefore it was possible to “learn” the connectivity associated with a given spanning tree by watching where packets came from. However the spanning tree itself was restrictive and often led to over-utilization of the links that were on the spanning tree and non-utilization of the links that weren't part of the spanning tree.
To overcome some of the limitations inherent in Ethernet networks implementing a spanning tree, a link state protocol controlled Ethernet network was disclosed in U.S. Pat. No. 7,688,756 filed Oct. 6, 2006, entitled “Provider Link State Bridging,” the content of which is hereby incorporated herein by reference. As described in greater detail in that application, rather than utilizing a learned network view at each node by using the Spanning Tree Protocol (STP) algorithm combined with transparent bridging, in a link state protocol controlled Ethernet network the bridges forming the mesh network exchange link state advertisements to enable each node to have a synchronized view of the network topology. This is achieved via the well understood mechanism of a link state routing system. The bridges in the network have a synchronized view of the network topology, have knowledge of the requisite unicast and multicast connectivity, can compute shortest path connectivity between any pair of bridges in the network, and can individually populate their forwarding information bases (FIBs) according to the computed view of the network.
When all nodes have computed their role in the synchronized view and populated their FIBs, the network will have a loop-free unicast tree to any given bridge from the set of peer bridges (those that require communication to that bridge for whatever reason); and a both congruent and loop-free point-to-multipoint (p2mp) multicast tree from any given bridge to the same set or subset of peer bridges per service instance hosted at the bridge. The result is the path between a given bridge pair is not constrained to transiting the root bridge of a spanning tree and the overall result can better utilize the breadth of connectivity of a mesh. In essence every bridge roots one or more trees which define unicast connectivity to that bridge, and multicast connectivity from that bridge.
When customer traffic enters a provider network, the customer MAC address (C-MAC DA) is resolved to a provider MAC address (B-MAC DA), so that the provider may forward traffic on the provider network using the provider MAC address space. Additionally, the network elements on the provider network are configured to forward traffic based on Virtual LAN ID (VID) so that different frames addressed to the same destination address but having different VIDs may be forwarded over different paths through the network. In operation, a link state protocol controlled Ethernet network may associate one VID range with shortest path forwarding, such that unicast and multicast traffic may be forwarded using a VID from that range, and traffic engineering paths may be created across the network on paths other than the shortest path, and forwarded using a second VID range.
In order to add true carrier class features to link state protocol controlled Ethernet, certain Operations, Administration, and Management (OAM) features are desirable. Ethernet OAM as currently defined in IEEE standard 802.1ag “Connectivity Fault Management”, defines a set of connectivity fault management protocols for use in Ethernet networks. These include: continuity check, link trace, and loopback protocols. The 802.1ag standard has been extended to include performance monitoring metrics and messages. This standard is reflected at ITU-T SG 13, Y.1731—“Requirements for OAM in Ethernet Networks”. But the mechanisms described in these standards are not directly applicable to link state protocol Ethernet networks because of some differences in addressing and VLAN semantics and usage between the standards and the link state protocol Ethernet networks. It is desirable to incorporate OAM features for fault identification, isolation, troubleshooting, and performance monitoring purposes into link state protocol Ethernet networks.